cuvier's definition of species. 51 



from one another, or from common ancestors, or which are 

 as similar to these as the latter are among themselves." 



In dealing with this matter, Cuvier reasoned in the 

 following manner: — "In those organic individuals, of which 

 we know that they are descended from one and the same 

 common form of ancestors — in which, therefore, their com- 

 mon ancestry is empirically proved — there can be no doubt 

 that they belong to one species, whether they differ much or 

 little from one another, or whether they are almost alike or 

 very unlike. Moreover, all those individuals also belong to 

 this species which differ no more from the latter (those 

 proved to be derived from a common stock) than these differ 

 from one another." In a closer examination of this definition 

 of species given by Cuvier, it becomes at once evident that 

 it is neither theoretically satisfactory nor practically appli- 

 cable. Cuvier, with this definition, began to move in the 

 same circle in which almost all subsequent definitions 

 of species have moved, through the assumption of -their 

 immutability. 



Considering the extraordinary authority which George 

 Cuvier has gained in the science of organic nature, and in con- 

 sequence of the almost unlimited supremacy which his views 

 exercised in zoology, during the first half of our century, it 

 seems appropriate here to examine his influence a little more 

 closely. This is all the more necessary as we have to com- 

 bat, in Cuvier, the most formidable opponent to the Theory 

 of Descent and the monistic conception of nature. 



One of the many and great merits of Cuvier is that he 

 stands forth as the founder of Comparative Anatomy. While 

 Linnaeus established the distinction of species, genera, orders, 

 and classes mostly upon external characters, and upon sepa- 



